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Sep 22, 2013
09/13

by
E. Fabiano; F. Della Sala

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We construct a reference benchmark set for atomic and molecular random-phase-approximation (RPA) correlation energies in a density functional theory (DFT) framework at the complete basis set limit. This set is used to evaluate the accuracy of some popular extrapolation schemes for RPA all-electron molecular calculations. The results indicate that for absolute energies accurate results, clearly outperforming raw data, are achievable with two-point extrapolation schemes based on quintuple- and...

Source: http://arxiv.org/abs/1302.5213v1

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40

Sep 22, 2013
09/13

by
F. Della Sala; S. Blumstengel; F. Henneberger

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We study the physisorption of organic oligomers on the ZnO($10\bar{1}0$) surface using first-principles density-functional theory and non-empirical embedding methods. We find that both in-plane location and orientation of the molecules are completely determined by the coupling of their quadrupole moments to the periodic dipolar electric field present at the semiconductor surface. The adsorption is associated with the formation of a molecular dipole moment perpendicular to the surface, which...

Source: http://arxiv.org/abs/1101.4076v1

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0.0

Jun 30, 2018
06/18

by
E. Fabiano; S. Laricchia; F. Della Sala

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We extend the frozen density embedding theory to non-integer subsystems' particles numbers. Different features of this formulation are discussed, with special concern for approximate embedding calculations. In particular, we highlight the relation between the non-integer particle-number partition scheme and the resulting embedding errors. Finally, we provide a discussion of the implications of the present theory for the derivative discontinuity issue and the calculation of chemical reactivity...

Topics: Physics, Chemical Physics, Other Condensed Matter, Condensed Matter

Source: http://arxiv.org/abs/1403.4449

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2.0

Jun 28, 2018
06/18

by
E. Fabiano; F. Della Sala; I. Grabowski

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Using the observed proportionality of CCSD(T) and MP2 correlation interaction energies [I. Grabowski, E. Fabiano, F. Della Sala, Phys. Chem. Chem. Phys. 15, 15485 (2013)] we propose a simple scaling procedure to compute accurate interaction energies of non-covalent complexes. Our method makes use of MP2 and CCSD(T) correlation energies, computed in relatively small basis sets, and fitted scaling coefficients to yield interaction energies of almost complete basis set limit CCSD(T) quality....

Topics: Chemical Physics, Physics, Condensed Matter, Materials Science

Source: http://arxiv.org/abs/1507.03339

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Jul 20, 2013
07/13

by
S. Laricchia; E. Fabiano; F. Della Sala

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We apply the frozen density embedding method, using a full relaxation of embedded densities through a freeze-and-thaw procedure, to study the electronic structure of several benchmark ground-state charge-transfer complexes, in order to assess the merits and limitations of the approach for this class of systems. The calculations are performed using both semilocal and hybrid exchange-correlation (XC) functionals. The results show that embedding calculations using semilocal XC functionals yield...

Source: http://arxiv.org/abs/1304.4417v1

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20

Sep 21, 2013
09/13

by
E. Fabiano; L. A. Constantin; F. Della Sala

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We review the performance of the PBEint GGA functional (Phys. Rev. B 2010, 82, 113104) recently proposed to improve the description of hybrid interfaces, and we introduce its one-parameter hybrid form (hPBEint). We consider different well established benchmarks for energetic and structural properties of molecular and solid-state systems as well as model systems and newly developed benchmark sets for dipole moments and metal-molecule interactions. We find that PBEint and hPBEint (with 16.67%...

Source: http://arxiv.org/abs/1301.5808v1

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0.0

Jun 29, 2018
06/18

by
E. Fabiano; P. Gori-Giorgi; M. Seidl; F. Della Sala

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We have tested the original interaction-strength-interpolation (ISI) exchange-correlation functional for main group chemistry. The ISI functional is based on an interpolation between the weak and strong coupling limits and includes exact-exchange as well as the G\"orling-Levy second-order energy. We have analyzed in detail the basis-set dependence of the ISI functional, its dependence on the ground-state orbitals, and the influence of the size-consistency problem. We show and explain some...

Topics: Chemical Physics, Condensed Matter, Physics, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1609.06045

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0.0

Jun 30, 2018
06/18

by
S. Śmiga; E. Fabiano; L. A. Constantin; F. Della Sala

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The development of semilocal models for the kinetic energy density (KED) is an important topic in density functional theory (DFT). This is especially true for subsystem DFT, where these models are necessary to construct the required non-additive embedding contributions. In particular, these models can also be efficiently employed to replace the exact KED in meta-Generalized Gradient Approximation (meta-GGA) exchange-correlation functionals allowing to extend the subsystem DFT applicability to...

Topics: Physics, Condensed Matter, Other Condensed Matter, Chemical Physics

Source: http://arxiv.org/abs/1702.04154

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4.0

Jun 26, 2018
06/18

by
E. Fabiano; L. A. Constantin; P. Cortona; F. Della Sala

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We propose global hybrid approximations of the exchange-correlation (XC) energy functional which reproduce well the modified fourth-order gradient expansion of the exchange energy in the semiclassical limit of many-electron neutral atoms and recover the full local density approximation (LDA) linear response. These XC functionals represent the hybrid versions of the APBE functional [Phys. Rev. Lett. 106, 186406, (2011)] yet employing an additional correlation functional which uses the...

Topics: Chemical Physics, Condensed Matter, Physics, Materials Science

Source: http://arxiv.org/abs/1501.01760

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0.0

Jun 30, 2018
06/18

by
E. Fabiano; L. A. Constantin; F. Della Sala

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We performed a benchmark study on a series of dihydrogen bond complexes and constructed a set of reference bond distances and interaction energies. The test set was employed to assess the performance of several wave-function correlated and density functional theory methods. We found that second-order correlation methods describe relatively well the dihydrogen complexes. However, for high accuracy inclusion of triple contributions is important. On the other hand, none of the considered density...

Topics: Physics, Chemical Physics, Materials Science, Condensed Matter

Source: http://arxiv.org/abs/1407.1998

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0.0

Jun 30, 2018
06/18

by
L. A. Constantin; E. Fabiano; A. Terentjevs; F. Della Sala

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We propose a simple gradient-dependent bound for the exchange-correlation energy (sLL), based on the recent non-local bound derived by Lewin and Lieb. We show that sLL is equivalent to the original Lieb-Oxford bound in rapidly-varying density cases but it is tighter for slowly-varying density systems. To show the utility of the sLL bound we apply it to the construction of simple semilocal and non-local exchange and correlation functionals. In both cases improved results, with respect to the use...

Topics: Physics, Chemical Physics, Other Condensed Matter, Condensed Matter

Source: http://arxiv.org/abs/1411.1579

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0.0

Jun 29, 2018
06/18

by
L. A. Constantin; E. Fabiano; F. Della Sala

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We introduce a novel non-local ingredient for the construction of exchange density functionals: the reduced Hartree parameter, which is invariant under the uniform scaling of the density and represents the exact exchange enhancement factor for one- and two-electron systems. The reduced Hartree parameter is used together with the conventional meta-generalized gradient approximation (meta-GGA) semilocal ingredients (i.e. the electron density, its gradient and the kinetic energy density) to...

Topics: Chemical Physics, Condensed Matter, Physics, Other Condensed Matter

Source: http://arxiv.org/abs/1608.08809

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Sep 21, 2013
09/13

by
L. A. Constantin; E. Fabiano; F. Della Sala

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We discuss, simplify, and improve the spin-dependent correction of L.A. Constantin et al., Phys. Rev. B 84, 233103, for atomization energies, and develop a density parameter of the form $v\propto |\nabla n|/n^{10/9}$, found from the statistical ensemble of one-electron densities. The here constructed exchange-correlation generalized gradient approximations (GGAs), named zvPBEsol and zvPBEint, show a broad applicability, and a good accuracy for many applications, because these corrected...

Source: http://arxiv.org/abs/1301.7576v1

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0.0

Jun 30, 2018
06/18

by
F. Della Sala; E. Fabiano; L. A. Constantin

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We show that the Kohn-Sham positive-definite kinetic energy (KE) density significantly differs from the von Weizs\"acker (VW) one at the nuclear cusp as well as in the asymptotic region. At the nuclear cusp, the VW functional is shown to be linear and the contribution of p-type orbitals to the KE density is theoretically derived and numerically demonstrated in the limit of infinite nuclear charge, as well in the semiclassical limit of neutral large atoms. In the latter case, it reaches 12...

Topics: Physics, Chemical Physics, Other Condensed Matter, Atomic Physics, Condensed Matter

Source: http://arxiv.org/abs/1411.3804

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1.0

Jun 29, 2018
06/18

by
L. A. Constantin; E. Fabiano; F. Della Sala

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We investigate the behavior of the kinetic and the exchange energy densities near the nuclear cusp of atomic systems. Considering hydrogenic orbitals, we derive analytical expressions near the nucleus, for single shells, as well as in the semiclassical limit of large non-relativistic neutral atoms. We show that a model based on the helium iso-electronic series is very accurate, as also confirmed by numerical calculations on real atoms up to two thousands electrons. Based on this model, we...

Topics: Atomic Physics, Materials Science, Condensed Matter, Physics, Other Condensed Matter

Source: http://arxiv.org/abs/1603.09484

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Jun 30, 2018
06/18

by
S. Laricchia; L. A. Constantin; E. Fabiano; F. Della Sala

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We test Laplacian-level meta-generalized gradient approximation (meta-GGA) non-interacting kinetic energy functionals based on the fourth-order gradient expansion (GE4). We consider several well known Laplacian-level meta-GGAs from literature (bare GE4, modified GE4, and the MGGA functional of Perdew and Constantin [Phys. Rev. B \textbf{75},155109 (2007)]), as well as two newly designed Laplacian-level kinetic energy functionals (named L0.4 and L0.6). First, a general assessment of the...

Topics: Physics, Chemical Physics, Other Condensed Matter, Condensed Matter

Source: http://arxiv.org/abs/1403.4448

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2.0

Jun 27, 2018
06/18

by
S. Śmiga; E. Fabiano; S. Laricchia; L. A. Constantin; F. Della Sala

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We analyze the methodology and the performance of subsystem density functional theory (DFT) with meta-generalized gradient approximation (meta-GGA) exchange-correlation functionals for non-bonded systems. Meta-GGA functionals depend on the Kohn-Sham kinetic energy density (KED), which is not known as an explicit functional of the density. Therefore, they cannot be directly applied in subsystem DFT calculations. We propose a Laplacian-level approximation to the KED which overcomes the problem...

Topics: Chemical Physics, Physics, Condensed Matter, Other Condensed Matter

Source: http://arxiv.org/abs/1505.00598

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Jun 30, 2018
06/18

by
I. Grabowski; E. Fabiano; A. Teale; S. Śmiga; A. Buksztel; F. Della Sala

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The performance of correlated optimized effective potential (OEP) functionals based on the spin-resolved second-order correlation energy is analyzed. The relative importance of singly- and doubly- excited contributions as well as the effect of scaling the same- and opposite- spin components is investigated in detail comparing OEP results with Kohn-Sham (KS) quantities determined via an inversion procedure using accurate ab initio electronic densities. Special attention is dedicated in...

Topics: Physics, Chemical Physics, Materials Science, Condensed Matter

Source: http://arxiv.org/abs/1407.8096

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0.0

Jun 28, 2018
06/18

by
E. Fabiano; L. A. Constantin; A. Terentjevs; F. Della Sala; P. Cortona

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We assess the Tognetti-Cortona-Adamo (TCA) generalized gradient approximation correlation functional [J. Chem. Phys. 128:034101 (2008)] for a variety of electronic systems. We find that, even if the TCA functional is not exact for the uniform electron gas, it is very accurate for the jellium surface correlation energies and it gives a realistic description of the quantum oscillations and surface effects of various jellium clusters, that are important model systems in computational chemistry and...

Topics: Materials Science, Chemical Physics, Condensed Matter, Physics

Source: http://arxiv.org/abs/1510.01604

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Sep 23, 2013
09/13

by
T. A. Niehaus; M. Rohlfing; F. Della Sala; A. Di Carlo; Th. Frauenheim

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We present a tight-binding based GW approach for the calculation of quasiparticle energy levels in confined systems such as molecules. Key quantities in the GW formalism like the microscopic dielectric function or the screened Coulomb interaction are expressed in a minimal basis of spherically averaged atomic orbitals. All necessary integrals are either precalculated or approximated without resorting to empirical data. The method is validated against first principles results for benzene and...

Source: http://arxiv.org/abs/cond-mat/0411024v1

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4.0

Jun 29, 2018
06/18

by
L. A. Constantin; A. Terentjevs; F. Della Sala; P. Cortona; E. Fabiano

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Using the semiclassical neutral atom theory, we extend to fourth order the modified gradient expansion of the exchange energy of density functional theory. This expansion can be applied both to large atoms and solid-state problems. Moreover, we show that it can be employed to construct a simple and non-empirical generalized gradient approximation (GGA) exchange-correlation functional competitive with state-of-the-art GGAs for solids, but also reasonably accurate for large atoms and ordinary...

Topics: Chemical Physics, Materials Science, Condensed Matter, Physics, Other Condensed Matter

Source: http://arxiv.org/abs/1601.06494

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Jun 29, 2018
06/18

by
L. A. Constantin; E. Fabiano; J. M. Pitarke; F. Della Sala

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Semilocal density functional theory is the most used computational method for electronic structure calculations in theoretical solid-state physics and quantum chemistry of large systems, providing good accuracy with a very attractive computational cost. Nevertheless, because of the non-locality of the exchange-correlation hole outside a metal surface, it was always considered inappropriate to describe the correct surface asymptotics. Here, we derive, within the semilocal density functional...

Topics: Materials Science, Condensed Matter, Other Condensed Matter

Source: http://arxiv.org/abs/1601.05537

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Sep 21, 2013
09/13

by
V. Fiorentini; F. Bernardini; F. Della Sala; A. Di Carlo; P. Lugli

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Huge built-in electric fields have been predicted to exist in wurtzite III-V nitrides thin films and multilayers. Such fields originate from heterointerface discontinuities of the macroscopic bulk polarization of the nitrides. Here we discuss the background theory, the role of spontaneous polarization in this context, and the practical implications of built-in polarization fields in nitride nanostructures. To support our arguments, we present detailed self-consistent tight-binding simulations...

Source: http://arxiv.org/abs/cond-mat/9905186v1

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Jul 20, 2013
07/13

by
A. Tanwar; E. Fabiano; P. E. Trevisanutto; L. Chiodo; F. Della Sala

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We present a theoretical study of the ionization potential in small anionic gold clusters, using density functional theory, with and without exact-exchange, and many body perturbation theory, namely the G0W0 approach. We find that G0W0 is the best approach and correctly describes the first ionization potential with an accuracy of about 0.1 eV.

Source: http://arxiv.org/abs/1304.4355v1

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Sep 18, 2013
09/13

by
F. Della Sala; A. Di Carlo; P. Lugli; F. Bernardini; V. Fiorentini; R. Scholz; J. -M. Jancu

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The free-carrier screening of macroscopic polarization fields in wurtzite GaN/InGaN quantum wells lasers is investigated via a self-consistent tight-binding approach. We show that the high carrier concentrations found experimentally in nitride laser structures effectively screen the built-in spontaneous and piezoelectric polarization fields, thus inducing a ``field-free'' band profile. Our results explain some heretofore puzzling experimental data on nitride lasers, such as the unusually high...

Source: http://arxiv.org/abs/cond-mat/9809409v1

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Jun 29, 2018
06/18

by
Z. Yong; P. E. Trevisanutto; L. Chiodo; I. Santoso; A. R. Barman; T. C. Asmara; S. Dhar; A. Kotlov; A. Terentjevs; F. Della Sala; V. Olevano; M. Rübhausen; T. Venkatesan; A. Rusydi

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Titanium dioxide (TiO$_2$) has rich physical properties with potential implications in both fundamental physics and new applications. Up-to-date, the main focus of applied research is to tune its optical properties, which is usually done via doping and/or nano-engineering. However, understanding the role of $d$-electrons in materials and possible functionalization of $d$-electron properties are still major challenges. Herewith, within a combination of an innovative experimental technique, high...

Topics: Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1605.06887